Oddball for me, given I'm principally a mechanics tool guy.  I'm guessing MHF is Massey-Ferg?  What are the measurements indicators for, gas maybe?  Thanks.

We had this guy on here a while back, search for Massey Harris wrench in the search bar in the top right corner and it will show up.

It's the plow setting wrench, not recommended to dip the gas tank.

Isn't there a ford wrench like that too.

Yes, there is, and some still insist it is to measure fuel in the tank.

So the scale is to set plow depth?  Makes sense.

I have one of those in my show stock.  They were Massey Harris Ferguson for a limited time; 1953 -1957, I think.  Just going off the top of my head; it is in Rathbone's book.

I enjoyed the posts about the plow wrench, and when I saw one in a Topeka antique shop yesterday, I worked on getting it. 
I traded a (not old at all) $3 Plumb hatchet for it.  Told the lady she should tie a ribbon around it.
It is marked 9N17014 FoMoCo (in the oval) USA on the front and circle M 17 on the back.
Made me a happy guy.